Effects Of Chemical Herbicides On The Community Of Insect Enemies In Rice Fields

The effects of chemical herbicides on the community of insect enemies in rice fields and non-rice fields were studied in this paper. Meanwhile, some indoor experiments were carried out to reveal the killing effects of some commonly-used herbicides on the important natural enemies of rice insect pests, and supply evidences for the field study in this paper. The major results were concluded as follows:1. Effects of herbicides on the community of insect enemies in rice fieldsButachlor and Sindax were applied in different rice fields. The results indicated that different herbicides had different effects on the community of insect enemies in the treated fields. The species diversity and abundance of insect enemies were significantly lower in the rice field treated with Butachlor than in the unsprayed control. The diversity indexes and evenesses of the community of insect enemies reduced in several days after Butachlor was sprayed in the field. Compared with the unsprayed field, the populations of insect enemies which usually move at the bottom of rice clusters or above water surface, such as Coleosoma octomaculatum, Microvella horvathi, Cyrtorrhinus lividipenis and larvae of wolf spiders, reduced evidently, while those enemies which inhabit on rice leaves or at the middle and top of rice cane, such as Tetragnatha nitens, Tetragnatha maxillosa, Argiopinae inustus and Ummeliata insecticeps, were not impacted significantly in the treated field. The application of Sindax had no evidently negative effects on the community structure and diversity of insect enemies in the treated field.2. Effects of herbicides on the community of insect enemies in weed habitatsParaquat was applied to a weed habitat at a recommended dosage, and the effects of its application on the community of the insect enemies in the treated field were studied. The results indicated that the use of herbicide Paraquat would cause direct and/or indirect negative effects on the community of insect enemies in the weed habitat. The direct effects were that Paraquat would kill a number of natural enemies of insects and spiders, and the indirect effects were associated with the direct effects of Paraquat on the weed community in the treated field. As a result, it changed the species composition and the community structure of insect enemies in the weed habitat sprayed with Paraquat, and the diversity and abundance of this community were lower in the treated field than in the unsprayed control.3. Effects of chemical weeding on the community reestablishment of insect enemiesin the rice field adjoining to the treated weed habitat...